Speedo Internals

[TR3driver]

(how does one get email notification of posts to a topic

When you use the full reply screen (as opposed to the "quick reply" at the bottom of the thread), there is a check box for "Add this thread to my Watched Topics". If you mark that, you will get an email for each new post.

Sorry, no help with the "missing" spring, except to note that none of my speedos have had a spring there either. The pawl gets moved into contact by friction with the driving gear (hence the spring clip).

 

[jjbunn]

(how does one get email notification of posts to a topic

When you use the full reply screen (as opposed to the "quick reply" at the bottom of the thread), there is a check box for "Add this thread to my Watched Topics". If you mark that, you will get an email for each new post.

Sorry, no help with the "missing" spring, except to note that none of my speedos have had a spring there either. The pawl gets moved into contact by friction with the driving gear (hence the spring clip).

I will try it without the spring. The plastic moulding certainly looks like it is designed to have a spring attached at that point. However, I could find no end point on the rest of the speedo unit to which the spring would attach.

(Just spotted the "watched topics" option: thanks!)

 

[Guest]

It looks more like a guide arm for the reverse lock lever so it will always catch the wheel. I think it's curved back so it wont get caught on the metal plate when moving in or out.

 

[MDCanaday]

You are mistaken about not needing a spring, it will not function with out it. These little beggers will make you crazy unless your quite good with tweezers.....
MD(mad dog)

 

[Guest]

Julian,

I plan on starting my dash light bulb holder replacement tomorrow, I want to clean all my gauges too so I will take pictures of my speedometer guts for you. My speedometer/odometer worked fine during the 850 mile drive from Ohio. If it needs a spring, it should be in mine.

.

 

[dklawson]

You can make the odometer work on the bench for a short while without the spring but... eventually the pawl will come out of contact with the wheel and that will be the last mile it counts until you take the unit apart again.

The anchor point for the other end of the spring is typically a raised stamped tongue on the sheet metal frame. Could you post a few more pictures of your speedometer's internals? That might help us identify where the other end of the spring goes on your gauge.

These are very tiny delicate springs as MadDog said. They easily shoot across the room when you are trying to install them. If you do not have the old spring or other instruments to rob these parts out of, consider going to a thrift store and buying an old cassette tape player. Take the tape player apart for parts. Inside, either on the tape door mechanism or perhaps some of the linkages to position the tape you should find some very delicate springs that will be suitable substitutes for the Smiths ones. I've had to improvise more than once.

EDIT:
See my 11/05/07 post for updated information relative to the pawl spring and its application.

 

[jjbunn]

I put all the gauges back together last night, so I'm loath to dismantle the Speedo again. But now I know exactly what to do if it stops working once I get La Belge on the road (and who knows when that will be!).

I'm very interested to see what stirkle finds when he opens up his speedo.

 

[Guest]

I put all the gauges back together last night, so I'm loath to dismantle the Speedo again. But now I know exactly what to do if it stops working once I get La Belge on the road (and who knows when that will be!).

I'm very interested to see what stirkle finds when he opens up his speedo.

Julian,
There is no spring(s) involved as I suspected.

Inside of speedometer was not too bad and cleaned up nicely. A lot of dust inside the 2 green light covers. Glad I didn't order o-rings or gaskets, they are all in very good condition.

 

[dklawson]

<s>I won't retract the statement that there should be a spring there as every Smiths speedometer I've taken apart has had the spring or has stopped counting the miles if the spring is missing or disconnected.</s>

However, if Smiths found a way to do without the springs on later TRs... I have learned something new. When I take apart a later TR6 speedometer I'll remember this thread and be looking for how the odometer can function without the spring.

EDIT:
I MUST retract my statement in paragraph #1. See my 11/05/07 post for updated information relative to the pawl spring and its application.

 

[jjbunn]

I won't retract the statement that there should be a spring there as every Smiths speedometer I've taken apart has had the spring or has stopped counting the miles if the spring is missing or disconnected.

However, if Smiths found a way to do without the springs on later TRs... I have learned something new. When I take apart a later TR6 speedometer I'll remember this thread and be looking for how the odometer can function without the spring.

Well, this is quite a mystery. I'm relieved that stirkle's is the same as mine, which is from a '71 TR6, so quite early. Perhaps the spring is simply optional? Perhaps they used springs when they had them, and dispenses with them otherwise? A bit far-fetched, I know.

 

[dklawson]

I stand corrected and must retract my earlier post.

I contacted Anthony Rhodes and asked about the odometer pawl spring on later speedometers. His reply is below.

"Later odometers did not have the spring. The pawl was intended to lift away when running backward. The odometer will NOT accrue mileage when running in reverse. Older speedometers WILL accrue increasing mileage even when going backwards.

The pawl is kept in contact with the teeth only by the rotational friction of its center post.

-Tony"

 

[jjbunn]

I stand corrected and must retract my earlier post.

I contacted Anthony Rhodes and asked about the odometer pawl spring on later speedometers. His reply is below.

"Later odometers did not have the spring. The pawl was intended to lift away when running backward. The odometer will NOT accrue mileage when running in reverse. Older speedometers WILL accrue increasing mileage even when going backwards.

The pawl is kept in contact with the teeth only by the rotational friction of its center post.

-Tony"

Fascinating: many thanks for the research, Doug!